[原创]求助prep中的一道数学题

我是橙橙 · 发表于 2008-4-5 23:32:00

At a dinner party, 5 people are to be seated around a circular table. Two seating arrangements are considered different only when the positions of the people are different relative to each other. What is the total number of different possible seating arrangements for the group?

(A) 5

(B) 10

(C) 24

(D) 32

(E) 120

答案是C 一点思路都没有哦

A contractor combined x tons of a gravel mixture that contained 10 percent gravel G, by weight, with y tons of a mixture that contained 2 percent gravel G, by weight, to produce z tons of a mixture that was 5 percent gravel G, by weight. What is the value of x ?

(1) y = 10

(2) z = 16

答案选D 可我认为应该选C啊
请指点一下哦

我是橙橙 · 发表于 2008-4-5 23:41:00

大家帮帮忙哦！！

masonyxm · 发表于 2008-4-5 23:55:00

先答复第一题：应该是P4,4. 这类圆圈的排座，记得QYQ的数学题上说过，总人数减一个的P排序。圆圈的状况下 ABCDE和EABCD是同一种，所以是P4，4.

我是橙橙 · 发表于 2008-4-6 00:06:00

哦懂了！只要是圆圈的排序直接减1个再P就对了！！谢谢啊！

我是橙橙 · 发表于 2008-4-6 23:59:00

第二题有哪位XDJM能教教我吗？

xlyun · 发表于 2008-4-7 00:27:00

the answer is d. because there are three equations and three unknowns,

x*0.1+y*0.02=0.05z, x+y=z

(1)
x*0.1+y*0.02=0.05(x+y)and y=10 ,than x=....

(2)x*0.1+y*0.02=0.05(x+y),y=z-x and z=16 ,than x...

[原创]求助prep中的一道数学题

[原创]求助prep中的一道数学题

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